Allyl isothiocyanate sprays

ABSTRACT

An allyl isothiocyanate spray prepared by dissolving 0.1 to 10% by weight of an allyl isothiocyanate in liquefied carbon dioxide gas and charging the resulting solution into a pressure vessel under a pressurization so that the liquefied carbon dioxide gas can maintain liquid phase. The spray can practically be employed with safety for bacteriostatic or germicidal treatment or for quality preservation.

BACKGROUND OF THE INVENTION AND STATEMENT OF RELATED ART

This invention relates to allyl isothiocyanate sprays.

Allyl isothiocyanate is also referred to as allyl mustard oil andgenerally obtained by extraction from a raw material such as mustard andJapanese horseradish (Wasabia japonica Matusum) by steam distillation orby subjecting sodium thiocyanate and allyl chloride to distillation.

The thus obtained allyl mustard oil is primarily utilized as a flavoringagent for foods or as a raw material of pharmaceutical preparations.

The present inventors, having noted the properties of allyl mustard oiland use thereof for bacteriostatic or germicidal treatment or qualitypreservation, made extensive studies.

They found that satisfactory effect can be exhibited if allyl mustardoil is used even in a very small amount for the purpose ofbacteriostatic or germicidal treatment, etc.

However, allyl mustard oil is an oily liquid which develops peculiarirritating odor and has a comparatively low flash point, so that itinvolves a number of problems so as to be utilized widely. For example,when allyl mustard oil is used for bacteriostatic or germicidaltreatment, it must be vaporized, requiring a vaporizing apparatus forthat purpose. Besides, the vaporizing apparatus must indispensably beequipped with a safety device since a low-flash point oil is vaporized,so that the vaporizing apparatus will inevitably be enlarged andexpensive. Accordingly, the vaporizing apparatus cannot conveniently beutilized for other purposes than treating a great amount of materials tobe treated.

Spraying can be given as an expedient means of vaporizing allyl mustardoil. However, since ordinary spraying methods employ LPG (liquefiedpetroleum gas) or Freon gas as an atomizing medium, they involveproblems in the properties of such gas and in safety. When allyl mustardoil is sprayed using such gaseous medium, the aerosol thus formed comesto have a comparatively great particle size as big as that of mist tostain clothes or fabrics and besides it cannot be sprayed uniformly overa wide area. Accordingly, LPG and Freon cannot be employed for sprayingallyl mustard oil due to many inconveniences described above.

There is proposed another technique of spraying a solution of aprincipal spray agent dissolved in liquefied carbon dioxide gas. Thistechnique can give a very fine aerosol, but solubility of allyl mustardoil in liquefied carbon dioxide gas is not known and further this methodinvolves too many technical problems which must be solved, such asstrong irritating odor, correlation between the gaseous composition andthe practical bacteriostatic or germicidal effect of the aerosol, etc.,to be proposed as a practical method.

OBJECT AND SUMMARY OF THE INVENTION

This invention is directed to provide an allyl isothiocyanate sprayhaving overcome the above problems which is suitably used forbacteriostatic or germicidal treatment. More particularly, thisinvention is directed to provide a spray, prepared by dissolving allylisothiocyanate in a high-pressure liquefied carbon dioxide gas which isliquid and charging the resulting solution in liquid form in a pressurevessel, for example a cylinder or a storage tank, etc.

A first aspect of this invention relates to an allyl isothiocyanatespray, comprising a solution of 0.1 to 10% by weight of an allylisothiocyanate dissolved in liquefied carbon dioxide gas, charged in apressure vessel with a pressurization so that the liquefied gas canmaintain liquid phase.

A second aspect of this invention relates to an allyl isothiocyanatespray comprising a solution of allyl isothiocyanate dissolved in aliquefied carbon dioxide gas, which is prepared by charging 0.1 to 10%by weight of allyl isothiocyanate and then 99.9 to 90% by weight ofliquefied carbon dioxide gas to a pressure vessel so as to mix these twocomponents and provide a solution.

A third aspect of this invention relates to an allyl isothiocyanatespray in which said pressure vessel is equipped with an atomizing meansand the liquefied carbon dioxide gas serves as a propellant.

A fourth aspect of this invention relates to any of the above allylisothiocyanate sprays, in which the allyl isothiocyanate is an extractfrom Japanese horseradish or mustard or a prepurified product thereof.

In the spray according to this invention, the principal spray agentallyl isothiocyanate is dissolved homogeneously in liquefied carbondioxide gas. Meanwhile, since the liquefied carbon dioxide gas ischarged with pressurization into a pressure vessel, the spray, whenjetted, is allowed to expand quickly by the release from thehigh-pressure liquefied carbon dioxide gas, so that the allylisothiocyanate contained in the spray forms a very fine aerosol. Thethus finely divided allyl isothiocyanate stays floating in air over awide area for an extended time. Accordingly, for example, if a materialto be treated is contained in a closed vessel, a gaseous atmosphere ofhomogeneous composition can be produced to allow the material to betreated to be in contact uniformly with the allyl isothiocyanate andachieve bacteriostatic or germicidal treatment sufficiently.

According to the allyl isothiocyanate spray of this invention, noequipment for vaporizing allyl isothiocyanate is necessary. When thepresent allyl isothiocyanate spray is used in an actual application, itcan be utilized conveniently for various purposes only by carrying thepressure vessel to the desired spots. Besides, safety of the spray canbe secured, since the combustible allyl isothiocyanate is jettedtogether with inert carbon dioxide gas.

According to the present spray, a gaseous composition containing 0.1 to10% by weight of allyl isothiocyanate can sufficiently exhibitbacteriostatic or germicidal effect with no secondary affect such as ofscent or irritating odor. An allyl isothiocyanate content of less than0.1% by weight will sometimes bring about insufficient bacteriostatic orgermicidal effect; whereas that of more than 10% by weight is liable tocause secondary affect such as of strong irritating odor and the like.

Now that it was identified according to this invention that even a verysmall amount of allyl isothiocyanate can exhibit bacteriostatic orgermicidal effect, a minimum necessary amount of allyl isothiocyanatemay be dissolved in liquefied carbon dioxide gas to obviate such strongirritating odor in practical uses. If even such reduced level ofirritating odor is still felt offensive, a deodorizer may as necessarybe used at the same time or separately.

As allyl isothiocyanate, use may be made of any natural or syntheticallyl isothiocyanate. Allyl isothiocyanate is not restricted solely to asingle solid preparation consisting of 100% of allyl isothiocyanate, anda mixture oil containing allyl isothiocyanate, an extract of mustard orJapanese horseradish (usually contains above 90% of allylisothiocyanate), or a crude product may be used.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a graph showing a relationship between the temperature andpressure generally necessary for liquefied carbon dioxide gas to retainliquid phase.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Next, a preparation process and a preparation example of the sprayaccording to this invention as well as Test Examples when the spraysthus prepared were used for bacteriostatic or germicidal treatment willbe described below. It should be appreciated, however, that the presentinvention is not limited only to them.

A process for preparing the allyl isothiocyanate spray will be describedbelow.

To a 3 l volume pressure vessel is charged 0.1 to 10% by weight of allylmustard oil based on the liquefied carbon dioxide gas to be chargedlater. The amount of the allyl mustard oil can easily be calculated fromthe weight of the entire composition after liquefied carbon dioxide gasis charged with pressure to the vessel.

Subsequently, liquefied carbon dioxide gas is charged to the pressurevessel having already charged therein an allyl mustard oil in such anamount that the content of the allyl mustard oil may be 0.1 to 10% byweight. The relationship between the temperature and the pressuregenerally required for the liquefied carbon dioxide gas so as tomaintain liquid phase is as shown in FIG. 1. Namely, in order thatliquefied carbon dioxide gas can maintain liquid phase, a pressure ofabout 20 kgf/cm² or more at a temperature of -20° C., about 35 kgf/cm²or more at a temperature of 0° C., about 52 kgf/cm² or more at atemperature of 15° C. or about 73 kgf/cm² or more at a temperature of30° C. is required. When liquefied carbon dioxide gas is charged into apressure vessel with a pressure not lower than the prescribed level atthe corresponding temperature, a temperature change will occur uponcompletion of charging, causing a pressure change conforming to thecurve shown in FIG. 1, and thus the liquefied carbon dioxide gas canmaintain the liquid phase.

Since liquefied carbon dioxide gas is usually stored in a heat-insulatedcontainer under a pressure of about 20 kgf/cm² at a temperature of about-20° C., a predetermined amount of liquefied carbon dioxide gas ischarged therefrom maintaining this temperature into the pressure vesselpreliminarily charged with an allyl mustard in such an amount that thecontent of allyl mustard oil may be 0.1 to 10% by weight. If theresulting pressure vessel is left to stand at room temperature, forexample at 20° C., the pressure will be elevated to about 60 kgf/cm² ;whereas if the pressure vessel is left to stand at about 28° C., thepressure will be elevated to about 70 kgf/cm², providing a plenum fillstate in the pressure vessel with the liquefied carbon dioxide gas whilemaintaining liquid phase.

Meanwhile, when a liquefied carbon dioxide gas stored in aheat-insulated container under a pressure of about 20 kgf/cm² at atemperature of -20° C. is fed, for example, at a temperature of about28° C. to a pressure vessel preliminarily charged with a predeterminedamount of allyl mustard oil by means of a cryogenic gas pump, theliquefied carbon dioxide gas may be charged to a pressure of about 70kgf/cm² where it can retain liquid phase at about 28° C.

An allyl isothiocyanate spray comprising 0.1 to 10% by weight of anallyl mustard oil and 99.9 to 90% by weight of liquefied carbon dioxidegas can thus be obtained.

Preparation Example of Allyl Isothiocyanate Spray

According to the process as described above, the present inventorsprepared allyl mustard oil sprays by dissolving 1% by weight of an allylmustard oil in liquefied carbon dioxide gas under a pressure of 70kgf/cm² at a temperature of about 28° C. and by dissolving 3% by weightof an allyl mustard oil likewise in liquefied carbon dioxide gas under apressure of 70 kgf/cm² at a temperature of about 28° C., respectively.

Next, Test Examples using these sprays will be described.

TEST EXAMPLE 1

About 1 kg of chopped vegetables was almost equally divided into nineportions and packed in nine polyethylene film bags (thickness: 20 μm).Three of them were treated externally with the spray containing 1% byweight of allyl mustard oil for about one second through the sprayingmeans provided for the pressure vessel, and another three bags weretreated with the same spray for about 10 seconds. The rest wereuntreated as controls.

These samples were incubated at room temperature for 24 hours to comparechange in the freshness of the treated and untreated chopped vegetables.The results of observation are as shown in Table 1.

                  TABLE 1                                                         ______________________________________                                        Spraying     Results of observation                                           time         Browning  Odor development                                       ______________________________________                                        Untreated    3/3       3/3                                                     1 sec       1/3       0/3                                                    10 sec       0/3       0/3                                                    ______________________________________                                    

As shown in Table 1, positive quality preservation effect was exhibitedby treatment with the above sprays.

TEST EXAMPLE 2

Twenty-one packs of raw seaweed (Undaria pinnatifida) were divided intoseven groups each group consisting of three packs. One group wasuntreated as a control group, and the rest of the groups were treatedwith the sprays containing 1% by weight and 3% by weight of allylmustard oil under the conditions as shown in Table 2, respectively.These spraying treatments were carried out against the contents takenout of the packages and then packed in the same packages. The thustreated samples were incubated at a temperature of 10° C. and at ahumidity of 90% for two weeks at the longest to test the followingitems.

1) Fungus resistance: after 1, 7 and 14 days

2) Residual smell of Japanese horseradish: immediately after treatmentand after 1 day

3) General viable cell count: after 1 and 4 days

The test results are as shown in Table 3.

                  TABLE 2                                                         ______________________________________                                                 Ally mustard oil concentration                                                1% by weight                                                                              3% by weight                                             ______________________________________                                        Condition   1     2         3   4     5    6                                  No.                                                                           Spraying   10    20        30  10    20   30                                  time                                                                          (sec)                                                                         ______________________________________                                    

                                      TABLE 3                                     __________________________________________________________________________    Test result                                                                                     Residual horseradish                                                                    General viable cell                               Appearance*       odor      count                                             Treating                                                                            After                                                                             After                                                                             After                                                                             Immed.                                                                             After 1    After 4                                     condition                                                                           1 day                                                                             7 days                                                                            14 days                                                                           after                                                                              day  After 1 day                                                                         days                                        __________________________________________________________________________    Control                                                                             -   -   +   -    -    1.0 × 10.sup.6 /g                                                             1.9 × 10.sup.8 /g                     Treated                                                                             -   -   ±                                                                              ± -    6.4 × 10.sup.3 /g                                                             1.1 × 10.sup.7 /g                     group 1                                                                       Treated                                                                             -   -   ±                                                                              ± -    8.4 × 10.sup.2 /g                                                             8.5 × 10.sup.6 /g                     group 2                                                                       Treated                                                                             -   -   -   ± -    8.5 × 10.sup.2 /g                                                             2.9 × 10.sup.6 /g                     group 3                                                                       Treated                                                                             -   -   -   +    -    8.8 × 10.sup.3 /g                                                             1.8 × 10.sup.7 /g                     group 4                                                                       Treated                                                                             -   -   -   +    -    1.5 × 10.sup. 3 /g                                                            5.3 × 10.sup.5 /g                     group 5                                                                       Treated                                                                             -   -   -   +    -    9.6 × 10.sup.2 /g                                                             7.4 × 10.sup.4 /g                     group 6                                                                       __________________________________________________________________________     *Appearance was evaluated according to the following criteria:                +: Molding occurred substantially over the entire surface.                    ±: Molding occurred at some parts.                                         -: No change                                                             

As apparent from Table 3, in the treated groups using the above twotypes of sprays, not only molding was prevented but also the generalviable cell count was controlled to about 1/10² to 10³ compared with thecontrol groups, showing a positive bacteriostatic effect. On the otherhand, although the odor of Japanese horseradish was identifiedimmediately after treatment proportional to the intensity of treatment,the odor was diminished to a undetectable degree after 1 day. Thissuggests that the original taste or flavor of the food may notsubstantially be affected.

What is claimed is:
 1. A method of making an allyl isothiocyanateaerosol comprisingdissolving 0.1 to 10% by weight of an allylisothiocyanate in liquid carbon dioxide in a pressurized vessel to forma solution; and discharging the solution from the pressurized vesselwhereby the liquid carbon dioxide acts as a propellant to form the allylisothiocyanate aerosol.
 2. An allyl isothiocyanate solution for use toform a bacteriostatic or germicidal aerosol comprising 0.1 to 10% byweight of allyl isothiocyanate dissolved in 99.9 to 90% by weight ofliquid carbon dioxide.
 3. An allyl isothiocyanate aerosol made by theprocess ofdissolving 0.1 to 10% by weight of an allyl isothiocyanate inliquid carbon dioxide in a pressurized vessel to form a solution; anddischarging the solution from the pressurized vessel, whereby the liquidcarbon dioxide acts as a propellant to form the allyl isothiocyanateaerosol.
 4. An aerosol spray comprising 0.1 to 10% by weight of allylisothiocyanate dissolved in liquid carbon dioxide to form a solutionwherein the solution is under sufficient pressure to be in a liquidphase.